1. Field of the Invention
The present invention relates to a hand-guided impact hammer and hammer drill (percussion drill), the handgrip of which is spring mounted at the top and bottom to the hammer housing.
2. Description of Prior Art
With impact hammers and hammer drills of the aforementioned general type, the purpose of spring-mounting the handle is to keep away from the operator the vibrations which are inherently connected with the operation of such devices, and which are of particular significance with larger machines which have a correspondingly greater power, because in this case the vibrations are not only annoying, but also have a detrimental effect on the joints and the circulation.
Numerous constructions have been proposed for spring-mounting the handle. With all of these constructions, the spring mounting of the upper handgrip is essentially the same, or at least has similar characteristics, as does the bottom spring mounting. For example, German Pat. No. 20 09 537 and German Offenlegungsschrift No. 31 21 882 (based on Japanese disclosure No. 55-99012 and corresponding to U.S. Pat. No. 4,401,167-Sekizawa et al. dated Aug. 30, 1983) disclose such impact hammers and hammer drills. With these heretofore known devices, the precise guideability of the hammer required during operation demands a relatively hard spring-mounting. However, this has associated with it the drawback that the vibration of the hammer housing is insufficiently dampened for the operator. If, on the other hand, the spring-mounting is made relatively soft in order to achieve sufficient damping of the vibrations, this is done at the expense of the precise guideability, and when a lot of pressure is applied to the handle, the spring-mounting can give or deflect to such an extent that parts of the handle contact the hammer housing and generate jarring blows. The same conditions occur when a softly spring-mounted handle is pressed to the side, which occurs rather frequently when such devices are used.
An object of the present invention is to design impact hammers and hammer drills of the aforementioned general type in such a way that on the one hand, during normal operation, an optimum damping of vibrations is achieved, in other words, the acceleration from the housing to the operator is considerably reduced, and on the other hand, even during great pressure upon the handle, and during lateral twisting of the handle, no direct contact can occur between parts of the handle and parts of the housing; and, moreover, that at all times the hammer can be efficiently guided, even when larger work tools are used, such as drill bits, spade tools, etc.